An electrolyte solution comprising an alkali metal bis (oxalato)borate salt

Abstract

Described is an electrolyte solution that contains an alkali-metal bis(oxalato)borate salt. Also described is a method for preparing such an electrolyte solution and to a battery cell that includes the electrolyte.

1 . An electrolyte solution comprising:
 an alkali-metal bis(oxalato)borate salt, wherein the alkali metal ion is selected from sodium (Na + ) and potassium (K + )   an organic solvent comprising a pyrrolidone and/or a phosphoric acid ester compound.   
     
     
         2 . An electrolyte solution according to  claim 1 , wherein the organic solvent is N-alkyl-2-pyrrolidone having the following structure: 
       
         
           
           
               
               
           
         
         wherein R is selected from an alkyl group comprising 1-8 carbon atoms. 
       
     
     
         3 . The electrolyte solution according to  claim 1 , wherein the organic solvent is N-methyl-2-pyrrolidone (NMP). 
     
     
         4 . The electrolyte solution according to  claim 1 , wherein the organic solvent is trialkyl phosphate having the following structure: 
       
         
           
           
               
               
           
         
         wherein R 1 , R 2  and R 3  are independently selected from an alkyl group comprising 1-6 carbon atoms. 
       
     
     
         5 . The electrolyte solution according to  claim 1 , wherein the organic solvent is trimethyl phosphate (TMP). 
     
     
         6 . The electrolyte solution according to  claim 1 , wherein said organic solvent comprises a mixture of N-methyl-2-pyrrolidone (NMP) and trimethyl phosphate (TMP). 
     
     
         7 . The electrolyte solution according to  claim 6 , wherein said organic solvent comprises N-methyl-2-pyrrolidone (NMP) and trimethyl phosphate (TMP) in a range of from 40:60 to 90:10. 
     
     
         8 . The electrolyte solution according to  claim 1 , wherein the concentration of the salt in said electrolyte solution is from 0.3 to 1.5 M. 
     
     
         9 . The electrolyte solution according to  claim 1 , wherein the conductivity of said electrolyte solution is above 4 mS/cm at a temperature of 23° C., 
     
     
         10 . A battery cell comprising at least one electrode and an electrolyte solution according to  claim 1 . 
     
     
         11 . The battery cell according to  claim 10 , wherein said electrode is a positive electrode comprising a Prussian blue analog material with the chemical formula Na 2 Fe 2 (CN) 6 . 
     
     
         12 . A method for preparing an electrolyte solution comprising:
 providing an alkali-metal bis(oxalato)borate salt, wherein the alkali metal ion is selected from sodium (Na + ) and potassium (K + )   dissolving said salt in an organic solvent comprising a pyrrolidone and/or a phosphoric acid ester compound.   
     
     
         13 . The method according to  claim 12 , wherein said salt is dissolved in said organic solvent in a concentration of from 0.3 to 1.5 M. 
     
     
         14 . The method according to  claim 12 , wherein the organic solvent is N-alkyl-2-pyrrolidone having the following structure: 
       
         
           
           
               
               
           
         
         wherein R is selected from an alkyl group comprising 1-8 carbon atoms. 
       
     
     
         15 . The method according to  claim 12 , wherein the organic solvent is trialkyl phosphate having the following structure: 
       
         
           
           
               
               
           
         
         wherein R 1 , R 2  and R 3  are independently selected from an alkyl group comprising 1-6 carbon atoms. 
       
     
     
         16 . The method according to, wherein the organic solvent is N-methyl-2-pyrrolidone (NMP) and/or trimethyl phosphate (TMP).